When patients are being ventilated mechanically on an intensive-care ward, for example, the patient to be ventilated is connected pneumatically to the ventilator by means of a breathing tube system. Because the breathing gas which is supplied to the patient must be adjusted with respect to temperature and humidity to the physiological needs of the patient, a respiratory humidifier is arranged in the inhalation or inspiration tube to warm and humidify the breathing gas. The respiratory humidifier comprises a liquid container filled with distilled water in the usual manner; the inhalation gas is conducted through this container, and its moisture content is thus increased.
To prevent moisture from condensing inside the breathing tube system, the inhalation tube and the expiration or exhalation tube are usually provided with electrical tube heaters, which warm the inhalation and exhalation gas flowing through them during operation. A loop of heating wire, for example, is used, which is integrated into the interior of the inhalation or exhalation tube, or the inhalation or exhalation tube is wrapped in each case with a coil of heating wire.
Breathing tube systems of this type are known from, for example, DE 10 2008 039 137 B3, DE 10 2007 003 455 A1, and DE 44 41 380 A1.
In the exhalation part of the breathing tube system, it is possible, especially in the case of patients with infectious diseases, to install filters to prevent the exhalation gas from carrying pathogens into the environment, which could result in additional patients or medical staff becoming infected. A filter of this type must be designed so that no condensate can form in it, because this would clog the filter and thus impair the filtering function. In the worst case, the ventilation function can also become defective, which can lead to negative results for the patient. Normally, the formation of condensate in the filter is prevented by means of additional heating devices and/or by means of water traps, as disclosed, for example, in U.S. Pat. No. 4,727,871. The general use of filter elements in ventilators is disclosed, for example, in U.S. Pat. No. 3,556,097.
GB 1 294 307 A describes a heatable anesthesia filter, which is used on the inhalation side of a respirator. A sleeve, in which a heater is integrated, is placed over a hermetically sealed container which contains a filter. The container is connected to the inhalation tubes by means of connecting pieces, one arranged at the beginning and the other at the end of the container.
The disadvantage of the above-mentioned breathing tube systems according to the prior art is that the heating of filters requires additional components such as cables, connectors, etc., which, because of the large number of cables and tubes to be connected, can lead to a loss of time and to the possible confusion of the operators. It can also be bothersome in the patient environment and can be susceptible to damage. The alternative use of unheated filters carries with it the danger of clogging attributable to the formation of condensate as previously described.